SANTA CLARA, Calif. -- He has a voice that has been described as both piercing and maniacal. He carries the nickname "Lord" from when he was an assistant at Stanford. He leaves messages on his voicemail at the office just before he falls asleep or if he wakes up in the middle of the night with a thought.

Vic Fangio is coordinator of the San Francisco 49ers' defense, which was the NFL's third best during the regular season and is the best of the four remaining teams in Sunday's conference championship games. The 49ers play the Falcons in Atlanta for the NFC title.

"He knows how to get the matchups he needs," defensive tackle Ray McDonald said of Fangio, who, like coach Jim Harbaugh, is in his second year with the 49ers. "He's a genius out there."

It may take a genius to stop a Falcons offense led by quarterback Matt Ryan that has the sixth-best passing offense and eighth-best overall offense.

More accurately, it will take Fangio's schemes, as utilized by linebacker Aldon Smith -- who was second in the league with 191/2 sacks (one behind Houston's J.J. Watt) -- All-Pro linebacker Patrick Willis and defensive tackle Justin Smith.

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"It all starts before the tackle is even attempted. You've got to establish the line of scrimmage and not give them big alleys and holes to run through."

Defense wins, they say, because if the other team doesn't score, the worst your team will have is a 0-0 tie. In three of the 49ers' last four games, however, they've had a 45-31 win over the Packers, a 42-13 loss to the Seahawks and a 41-34 win over the Patriots. They haven't come close to keeping the opponent from scoring. And scoring and scoring, for that matter.

"In playoff football," strong safety Donte Whitner said, "you're facing really good quarterbacks who know how to make adjustments. In the end, you've just got to make more stops than their defense does."

Aldon Smith didn't have a sack against the Packers. "It's just that they were throwing it fast," Fangio said. "He's rushing good. I think teams respect our rush. They throw it quick sometimes. It's not always stats. Don't look at the play-by-play after the game and make your conclusions. Watch the game."

Willis said to the Huffington Post two months ago: "We have one heartbeat. No person is bigger than the other. If we play together, we believe good things will happen."

Justin Smith was injured against New England on Dec. 16 and missed the last two regular- season games. Despite one doctor's prediction that Smith wouldn't play again until next season, he returned last weekend against the Packers. "He and Aldon played well," Fangio said.

Harbaugh, very much enamored of Smith's toughness and work habits, said: "The legend grows. What a player."

49ers wide receiver Michael Crabtree has voluntarily met with police in their investigation into an alleged sexual assault in a hotel, his attorney said Saturday. The 49ers said he made the trip to Atlanta.

Police had said they were investigating a sexual assault allegation involving Crabtree in a San Francisco hotel early last Sunday. Crabtree hasn't been detained or arrested. -- AP